As the electrical and electronic technology develops, high frequency isolated power transformation technique has been gradually more and more applied as an important moderate-speed versatile control means in the power grid. Phase shift modulation scheme (PSMS) based dual active bridge-isolated bidirectional DC/DC converter (DAB) has the characteristics of high power density, quick dynamic response, easily implementable soft switching, and bi-directional energy flow, thus, making it widely popular in the UPS, electric vehicle, and solid-state transformer, etc. Common means for controlling a DAB converter is via phase shift modulation, by means of generating a voltage square-wave with relative phase shift on the primary port and the secondary port of the high frequency converter, and by means of simultaneously controlling the relative phase shift between the primary and the secondary full-bridges driven by a switch obliquely orthogonal thereto to alter the duty ratio of the voltage square-wave, thus regulating the power flow via the converter. In accordance with the selected control variables, common modes for modulating a DAB converter include the single phase shift modulation (SPSM), dual phase shift modulation (DPSM), extended phase shift modulation (EPSM), and triple phase shift modulation (TPSM). Among these modes, the TPSM is the most general modulating mode, having three independent control variables, while the SPSM, DPSM, and EPSM may all be regarded as a simplified form of TPSM. Thus, the TPSM is the most versatile of them all, where rational constraint on the inter-relationship among the control variables may be exercised to decrease the effective value of the current passing through the converter to lower the current stress for the device during the transport of the same power by the DAB converter, therefore, the system efficiency may be elevated.
To increase the operational and transformational efficiency for the input and output power, realization of globally optimal operation is needed for the DAB. Further, how to realize the global optimization via close-loop control is the key to increase the operational performance of the DAB.